Matching this, an interlocking profile firmly affixed to the housing is positioned on its underside of the housing, and across from it at a distance is a displaceable securing lock that is spring-loaded toward the interlocking profile. The securing lock includes on its end away from the interlocking profile a shaped drawbar eye for engagement with an actuation tool. The housing side wall above the securing lock and extending upward extends at least with its lower area in a plane perpendicular to the displacement direction of the securing lock, and includes in this area a shaped tool-guide channel with its mouth pointed toward the drawbar eye on the securing lock.